How is the evolution of walrus tusks classified in relation to ancestral pinniped traits?

A derived trait that evolved within the walrus lineage

The tusks are considered a derived trait, meaning they evolved specifically within the walrus evolutionary line (*Odobenidae*) after it separated from the ancestors of modern seals and sea lions. The fossil evidence, particularly concerning forms like *Pontolis magnus*, shows that immediate ancestors of the Odobenids possessed the foundational body structure suitable for marine life but lacked these enormous ivory projections. This clearly indicates that the dental armament was not an ancient characteristic inherited from the earliest pinnipeds but rather a specialized adaptation that developed later, correlating perhaps with the need to access food in increasingly ice-covered environments.